Retaining structures and bridges in unstable rock or soil slopes

Rockfall and landslide prevention and stabilisation as well as risk assessment are essential for the design, construction and maintenance of structures in unstable slopes. Roads, highways and railways are frequently running in landslide-prone areas which often are seismic zones as well. The paper underlines the influence of water and shear parameters on slope stability, and the importance of determining the residual shear strength. Creeping causes excessive lateral pressures on structures; details for calculation are presented in this paper. Building in unstable slopes requires engineering flexibility and structures which can be strengthened step by step if necessary. This involves semi-empirical design (“active design”) based on calculated risk and the observational method including contingency plans and long-term monitoring. Several case histories demonstrate this engineering philosophy which has proved suitable for nearly 50 years.